This invention is directed toward the measure of temperature, and more particularly toward a sensor for measuring temperature of well borehole environs in the vicinity of a borehole instrument that is conveyed along the borehole. The temperature sensor is removably disposed preferably within the wall of the borehole instrument. The sensor can be embodied in a wide variety of borehole exploration and testing equipment including measurement-while-drilling, logging-while-drilling, and wireline systems.